Evaluation Engineering - 21

PCIe cable or other high-speed interface.
For reference purposes, 2U RAID subsystems in the RF test & measurement
market typically cost between $20k to
$40k, consume about 200 W, and weigh
between 35 and 40 pounds.

M.2 and NVMe
In late 2013, the PCI-SIG (the organization
responsible for PCI Express) announced
the PCIe M.2 Specification Revision 1.0.
The M.2 Standard established the popular "stick of gum" format for low-cost,
high-performance NAND flash-based
SSDs. M.2 SSDs support both SATA III
6 Gbps and direct PCIe Gen 3 x 4 interfaces, which supports up to about 4 GB/
sec of bandwidth. The nonvolatile memory
express (NVMe) standard establishes a
set of protocols that run on top of PCIe
that enable M.2 and other PCIe interface
SSDs (e.g., 2.5-inch U.2 SSDs) to efficiently
communicate with a host CPU. NVMe
supports the essential services that the
operating system, applications, and users need to effectively use and manage
this new type of storage device. M.2 SSDs
today support read/write speeds up to 3.5
GB/sec, capacities up to 2 TB for the most
popular 22 mm W x 80 mm L (2280) size,
low power consumption (typically under
10W per SSD,) and consumer-level pricing.
Consequently, M.2 has rapidly become the
most popular format SSD for new PCs,
which bodes well for ongoing improvements in density and performance.

Growth of NAND Flash-based SSDs
In part due to the popularity of M.2 and
NVMe, NAND flash-based solid-state
drive (SSD) shipments have experienced
extremely rapid growth over the past few
years. SSD shipment growth is largely
coupled to the rapid growth in mobile
and cloud computing segments, both of
which place a premium on performance
(low latency and high throughput), size,
weight, and power (SWaP). SSD adoption

RADX

has driven SSD volumes which tends to
reduce prices, thereby reinforcing the
adoption cycle. Consequently, SSD shipments are poised to overtake hard disk
drive (HDD) shipments by 2021, when SSD
annual shipments are expected to exceed
350 million, according to 2017 report by
Statista.1

PXIe-based RF RPA and
SSD RAID modules
With its intrinsic scalability (to support
multiple, wideband RF channels) and
compact form factor, PXIe has become a
very popular format for wideband RF RPA
systems. With the advent of small, high
data rate, low-power, low-cost M.2 SSDs
that directly supports PCIe interface, it's
now possible to combine a 2, 4 or even 8 x
M.2 SSDs with a PCIe switch to produce
an extremely high-performance, highcapacity, cost-effective SSD PXIe RAID
module that occupies a single PXIe slot.
These "in-chassis" SSD RAID modules deliver storage capacities up to 16 TB per
module with sequential read and write
data rates of 5 GB/sec and up. SST RAID
modules are priced between $7K to $14K,
consume less than 50 W, and weigh less

than a pound. One can install multiple
SSD RAID modules to increase capacity
and performance using software RAID.
Accordingly, SSD RAID modules can effectively eliminate the need for external
RAID subsystems for most applications-
thereby reducing cost and SWaP-while
delivering equal or greater performance.
There are three companies making
COTS SSD RAID modules today, all of
which employ multiple M.2 SSDs and
support a PCIe Gen 3 x 8 interface. The
National Instruments (NI) PXIe-8267
and the Conduant, Inc. DM-4M.2-3U are
COTS, single-slot, PCIe Gen 3 x 8, SSD
RAID modules with four (4) M.2 SSDs per
module and published sequential write/
read benchmark performance in the 5 to
7 GB/sec range. The RADX Trifecta-SSD
supports 4 or 8 x 2 TB M.2 SSDs to provide
8 or 16 TB of storage per slot and 6.9 to
7.2 GB/sec sequential write/read (benchmark) performance.

No free lunch
Sadly, there is no such thing as a free
lunch in engineering. While SSDs often
"feel" like fast HDDs, because of their underlying NAND flash architecture, they

Manufacturer

SSD RAID module

M.2 SSDs/
module

Capacity

Write and read
performance

For more information

National Instruments

PXIe-8267

4

4 TB

5/5 GB/sec

https://bit.ly/2T94SDm

Conduant Inc.

DM-4M.2-3U

4

4/8 TB

5.8/7 GB/sec

https://bit.ly/2xthGLv

RADX

PXIe-4M.2F-xTB

4/8

8 TB/16 TB

6.9/7.2 GB/sec

https://bit.ly/308BWi2

AUGUST 2019 EVALUATIONENGINEERING.COM

21
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Evaluation Engineering

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